Room's volume is 600 m^3. There is 800 ppm (parts per million) of CO2 in the room.
Fresh air, with the CO2 concentration of 400 ppm starts flowing into the room at the rate of 40 m^3/min. The pressure in the room is constant, so an equal amount of stale air flows out as fresh air flows in, and the CO2 is evenly distributed.
a) Form the differential equation for the amount of CO2 in the room.
b) Solve this differential equation
c) What is the CO2 concentration of the room after fresh air has been flowing in for 30 minutes?